The present invention relates to a communication control apparatus, a communication control method therefor and a storage medium for storing a communication control program which are used in a communication between a client and a server.
There are many types of communications between a client and a server. For example, as shown in FIG. 5, a server 504 has clients, such as a mobile computer 503 connected to the server 504 through a LAN 506, a mobile computer 502 connected to the server 504 through a public telecommunication network 510 and a gateway 505, a mobile computer 501 connected to the server 504 through a mobile telephone 508, the public telecommunication network 510 and the gateway 505, etc.
Recently, personal computers have rapidly advanced with greater computing power in small-sized computers. Therefore, a high performance computer may be easily carried, that is to say, use of the mobile computer has become wide-spread.
On the other hand, when the mobile computer is used as a client of a server application program on the server, the configuration of the client may need to be modified according to the communication type because there are many types of communications between clients and servers. For example, the World-Wide Web (WWW) system is known in which a modification of the configuration is needed according to the connection type.
In the WWW system, a WWW browser program on the client requests an HTML document stored in the server based on an HTTP protocol. Then, the server sends the designated HTML document to the client and the WWW browser program displays the HTML document received from the server on a screen. In the WWW system, a server called a proxy server is provided between the client and the server. The WWW browser program in the client sends information to identify the requested HTML document to the proxy server. When the requested document is stored in a cache in the proxy server, the proxy server can send the requested HTML document to the client without accessing the server.
However, the user must set up the configuration of the WWW browser program when a gateway, such as the proxy server, is used. In other words, the user needs to set up the configuration of each program when there are a plurality of programs to be set up.
Further, there is an application program which can not be connected using multiple connection types. This application program needs to be re-written. That is to say, the client application program which is intended to communicate directly with the server can not be used in communication through the gateway. Therefore, full advantage of the mobile computer is not taken because the user is allowed to connect to the server using only one connection type.
Further, while the public telephone network is used to connect the client with the server, the network is frequently disconnected because the public telephone network is not designed for data communication but rather for speech communication. High quality high-speed data communication is not ensured. The network may also be disconnected as a result of the condition of a radio wave while the mobile telephone is used to connect the client with the server. The network may also be disconnected because of a failure of a communication apparatus on the network wherein a LAN is used to connect the client with the server.
It is an object of the present invention to provide a communication control for the client-server system that enables the client to connect with the server using any connection type without modification of any existing client application programs.
It is another object of the present invention to provide communication control which enables recovery from a disconnected communication without restarting the application program.
The above first object of the present invention is achieved by a communication control method. In the communication control method, a relay apparatus corresponding to a designated apparatus to be communicated with is determined based on relay definition information which relates information for specifying the apparatus to be communicated with to information for specifying the relay apparatus. Then, the relay connection with the determined relay apparatus is established.
The above second object of the present invention is achieved by an automatic re-connection of the relay connection when the relay connection is disconnected.